1. Field of the Invention
The present invention relates to an improved high-voltage interrupting switch or interrupter and an improved method and arrangement for providing reliable and efficient electrical connection and disconnection of the contacts. The present invention is an improvement over the switches disclosed and claimed in the following, commonly assigned U.S. Pat. Nos.: 4,342,978; 4,370,531; 4,460,886; 4,467,307; 4,490,707; 4,494,103; and 4,499,446 which are hereby incorporated by reference for all purposes.
2. Description of the Related Art
The aforementioned patents relate to various aspects of a high-voltage interrupting switch and a high-voltage interrupting module containing the switch. The switch includes contacts defining one or more contact pairs which are normally electrically interconnected by either direct engagement therebetween, or by interconection via a shearable or tearable metallic disc, membrane, or diaphragm. In preferred arrangements, one contact in each pair is stationary and the other contact is movable, although both may be movable. The contacts are rapidly separated by relative movement apart along a fixed line of direction to open a gap therebetween, thereby opening the switch. One of the contacts, preferably the stationary contact, contains a bore in which a piston is positioned.
In a specific arrangement of the interrupting module, a fusible element is provided in electrical shunt with the switch; the switch and the fusible element preferably residing within a common housing. When the switch is closed (i.e., when the contacts thereof are electrically interconected), the impedance of the current path through the switch is much lower than the impedance of the current path through the fusible element, and accordingly a negligible portion of the current flowing through the module flows through the fusible element. The switch is designed to carry much higher currents than the fusible element. Thus, the module has a high continuous current rating. When an overcurrent condition exists, the piston is arranged to be rapidly moved and drives the movable contact away from the stationary contact to disconnect and break the normal electrical interconnection. Upon opening of the switch, the contacts separate and current is rapidly commutated from the switch to the fusible element where it is interrupted. The switch is required to transfer or commutate high currents from the main current path of the switch to the fusible element. Specifically, the maximum instantaneous current that the switch can rapidly transfer into the fusible element can be a limiting factor regarding the maximum interrupting capability of the interrupting module and the capability to interrupt high-frequency currents. For higher voltage and current ratings, the mass of the movable portion of the switch is greater requiring increased operating forces to reduce the delay in moving the mass of the movable portion of the switch.
In specific arrangements of the switch, a second stationary contact is included. While the switch is closed, the movable contact and the second stationary contact are electrically interconnected in similar fashion as the first stationary contact. When the piston is moved, the movable contact moves away from the first stationary contact and is telescoped into a bore formed in the second stationary contact. This bore may be lined with an insulative sleeve and the movable contact may be covered with an insulative sleeve, so that such telescoping results in the formation of a second gap between the movable contact and the second stationary contact. The second gap is electrically insulated by the reception of the insulative sleeve of the movable contact within the insulative sleeve of the bore of the second stationary contact.
During operation, the movable contact moves rapidly away from the first stationary contact and through a passageway in an insulative liner, into which the piston may also enter. The piston entering the passageway in the liner compresses and extinguishes the arc that forms between the movable contact and the first stationary contact. The piston may be insulative in which case the first gap that is formed, between the end of the first stationary contact and the movable contact, is insulated by the reception of the piston within the insulative liner. In a preferred arrangement of the switch, the stationary contacts and the liner are engageably surrounded, and have their relative positions fixed, by an insulative housing, which maintains the stationary contacts and the liner end-to-end with the bores and the passageway being axially aligned.
Considering now in more detail the various manners in which the stationary contacts and the movable contact are electrically interconnected in the aforementioned patents, U.S. Pat. No. 4,342,978 in FIGS. 3 through 5 and U.S. Pat. No. 4,370,531 in FIGS. 2 and 3 illustrate interconnection between a stationary contact and a movable contact via direct engagement by partial telescoping of the movable contact into the stationary contact. The telescoping or sliding engagement is provided either by solid members or by fingers provided on the movable contact. In FIG. 6 of U.S. Pat. No. 4,342,978 and in FIGS. 4 and 5 of U.S. Pat. No. 4,370,531, an additional conductive member is utilized to provide electrical interconnection between the movable contact and the stationary contact; the additional conductive member being a metallic disk or membrane which is shearable or tearable upon movement of the piston as the movable contact moves away from the stationary contact. In U.S. Pat. No. 4,342,978, the additional conductive member is referred to as a diaphragm and is identifed by reference numeral 162 in FIGS. 6 and 7. The diaphragm 162 is brazed or soldered to a conductive member 78 with the combination providing the movable contact 58. The diaphragm 162 is also positioned into and attached to the groove 160 of the stationary contact 56. In FIG. 4 of U.S. Pat. No. 4,370,531, the member 112 is attached between one end of a tube 106 of the stationary contact 61 and one end of a rod 110 of the movable contact 60. As the contacts 60,61 are separated by movement of the piston, the member 112 is severed, ripped, torn, or otherwise rendered discontinuous at 112a; a portion 112b remaining attached to the stationary contact 61 and a portion 112c remaining attached to the movable contact 60. A second member 120 electrically interconnects the movable contact 60 to the second stationary contact 92. The member 120 is attached to the rod 110 of the movable contact 60 by a connector 122. A member 112' similar to the diaphragm 112 of FIG. 4 is illustrated in the arrangement of FIG. 5 of U.S. Pat. No. 4,370,531. In switches of this type, the member 112, 112' or 162 may also be brazed to the stationary contact to provide a suitable electrical connection.
While the aforementioned arrangements may be generally suitable for their intended use, it would be advantageous to provide reliable electrical interconnection of the contacts of such interrupting switches in a more efficient manner while reducing the operating force required to cause disconnection of the electrical interconnection and separation of the contacts, and avoiding the necessity of a frangible or shearable connection between the stationary and movable contacts to accomplish the electrical interconnection. Additionally, it would be advantageous to provide a lower cost method of interconnection of such contacts.